1,214 research outputs found

    The Linear Polarization of Sagittarius A* I. VLA Spectro-polarimetry at 4.8 and 8.4 GHz

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    Synchrotron radiation from active galactic nuclei (AGN) is often highly polarized. We present a search for linear polarization with the Very Large Array (VLA) at 4.8 GHz and 8.4 GHz from the nearest AGN, Sagittarius A*. As a part of this study we used spectro-polarimetric data that were sensitive to a rotation measure (RM) as large as 3.5 x 10^6 rad m^-2 at 4.8 GHz and 1.5 x 10^7 rad m^-2 at 8.4 GHz. The upper limit to the linear polarization of Sgr A* over a broad range of RM is 0.2% at both frequencies. We also present continuum observations with the VLA at 4.8 GHz which give an upper limit of 0.1% for RMs less than 10^4 rad m^-2. We conclude that depolarization is unlikely to occur in the Galacter Center scattering medium. However, it is possible for depolarization to occur in the accretion region of Sgr A* if the outer scale of turbulence is small enough. We also consider the implications of a very low intrinsic polarization for Sgr A*.Comment: 16 pages, 3 figures, accepted for publication in the Astrophysical Journal, August 20, 1999, Vol 521 #

    Additions to the plume moth fauna of The Bahamas (Lepidoptera: Pterophoridae) with description of four new species

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    Records of Bahamas plume moths (Lepidoptera: Pterophoridae) collected since 2011 are summarized and four new species described: Michaelophorus salensis Matthews, new species, Oidaematophorus androsensis Matthews, new species, Hellinsia bahamensis Matthews, new species, and Hellinsia lucayana Matthews, new species. Species accounts including illustrations of adults and genitalia, diagnoses, larval hosts, habitats, and distributions are provided. Of the 23 species found, new larval host associations are reported for two species while the life histories remain unknown for seven species

    Observations of plume moths on North Andros Island, Bahamas, and notes on new records and species previously recorded from the Bahamas (Lepidoptera: Pterophoridae)

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    Recent fieldwork on North Andros Island by the authors resulted in the collection of six species of Pterophoridae (Lepidoptera), five of which were previously unrecorded for the Bahamas in published accounts. Three additional species are noted for the Bahamian fauna based on specimens collected in the 1980s on other islands. Representative specimens are illustrated from North Andros along with genitalic images for species where these are not readily available in other publications. In addition, images of the larva and pupa are provided for a reared species for which the life history was previously unknown

    Investigation of the large-scale neutral hydrogen near the supernova remnant W28

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    The distribution and kinematics of neutral hydrogen have been studied in a wide area around the supernova remnant W28. A 2.5 x 2.5 arcdeg field centered at l = 6.5 arcdeg, b = 0 arcdeg was surveyed using the Parkes 64-m radio telescope (HPBW 14.7 arcmin at lambda 21 cm). Even though W28 is located in a complex zone of the Galactic plane, we have found different HI features which are evidence of the interaction between W28 and its surrounding gas.Comment: 7 files into a tar.gz file (the Latex file of manuscript, 5 jpg figures, 1 style file: aastex.cls

    Radio astronomy

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    The following subject areas are covered: (1) scientific opportunities (millimeter and sub-millimeter wavelength astronomy; meter to hectometer astronomy; the Sun, stars, pulsars, interstellar masers, and extrasolar planets; the planets, asteroids, and comets; radio galaxies, quasars, and cosmology; and challenges for radio astronomy in the 1990's); (2) recommendations for new facilities (the millimeter arrays, medium scale instruments, and small-scale projects); (3) continuing activities and maintenance, upgrading of telescopes and instrumentation; (4) long range programs and technology development; and (5) social, political, and organizational considerations

    Setting a precautionary catch limit for Antarctic krill

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    A revised precautionary catch limit for Antarctic krill (Euphausia superba) in the Scotia Sea of 4 million tons was recently adopted by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). The limit was based on a total biomass of 44.3 million tons, as estimated from an acoustic and net survey of krill across the Scotia Sea sector of the Southern Ocean, and a harvest rate of 9.1%, as determined from an analysis of the risks of exceeding defined conservation criteria. We caution, however, that before the fishery can expand to the 4-inillion-ton level it will be necessary to establish mechanisms to avoid concentration of fishing effort, particularly in proximity to colonies of land-breeding krill predators, and to consider the effects of krill immigrating into the region from multiple sources

    Cutting Ties with Pro-Ana: A Narrative Inquiry Concerning the Experiences of Pro-Ana Disengagement from Six Former Site Users.

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    Websites advocating the benefits of eating disorders (“Pro-Ana”) tend to reinforce and maintain restrictive eating and purging behaviors. Yet remarkably, no study has explored individual accounts of disengagement from these sites and the associated meanings. Using narrative inquiry, this study sought to address this gap. From the interviews of six women, two overarching storylines emerged. The first closely tied disengagement to recovery with varying positions of personal agency claimed: this ranged from enforced and unwelcomed breaks that ignited change, to a personal choice that became viable through the development of alternative social and personal identities. A strong counternarrative to “disengagement as recovery” also emerged. Here, disengagement from Pro-Ana was storied alongside a need to retain an ED lifestyle. With “recovery” being just one reason for withdrawal from Pro-Ana sites, clinicians must remain curious about the meanings individuals ascribe to this act, without assuming it represents a step toward recovery.Peer reviewedFinal Accepted Versio
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